Although a purchaser of turntable playback recording equipment can spend considerable sums of money to obtain high quality playback of records, which expenses include the turntable, the stylus, the amplifier and the speakers and although a whole audio industry has developed to provide highly engineered electronic components therefor including those listed above, all such high fidelity equipment can be to a large extent nullified if the mechanical sound pick-up is improperly or inaccurately done. For example, the axis of the cutting stylus shaft assembly is generally aligned tangent to the groove being cut in the record master. Accordingly, unless the stylus cartridge is properly positioned so as to be tangentially disposed to the record groove or grooves on the record on the turntable and unless there is a proper stylus overhang which duplicates as closely as possible, the position of the stylus that cut the record master, then tracking error and sound distortion in playback of such record can result.
The mathematics and geometry underlying this tangential relationship was first explored by H. G. Baerwald in his article appearing in the December, 1941 issue of the "Journal of the Society of Motion Picture Engineers". The article discussed the mathematical requirements for the tangential relationship and commented on the audible effects of tangential misalignment of the playback stylus. Though cartridge alignment has been largely ignored for many years, the development of audio playback systems of high resolution capabilities has given new emphasis to the importance of cartridge alignment.
The above Baerwald Article stated that for a pivot type tone arm on a 12" diameter record, the overhang of the stylus should be such that would cause the stylus to cross over two points on such record so as to provide the least average tracking error of the stylus in the record grooves. The Baerwald Article located these points, called "null points" on circles of radii respectively of 2.600 and 4.760 inches from the spindle or axis of the turntable. The difficulty has been to establish where on these circles or one of them, should the associated stylus arm be adjusted, in length, so as to have an accurate overhang for such pivotable stylus arm and turntable. That is, the difficulty has been to locate the correct null point or points for a turntable-stylus arm assembly, which correctly located null point(s) is herein designated as a "geopoint" or "geopoints". To locate such geopoints, extensive calculations and expensive electronic equipment have been employed in a multistep, lengthy process and still there has been difficulty in obtaining accurate location of such geopoints.
Further the tangential alignment of the stylus cartridge has provided additional, if secondary, difficulty. And there has heretofore been no rapid and accurate alternative to the above prior art and there is a need and market for a method and apparatus for determining stylus location and alignment, which overcomes the above shortcomings.
There has now been discovered an apparatus which translates the rather complex mathematics and geometry of proper stylus positioning and alignment into a relatively quick and easy method for the layman and consumer as well as the audio industry. By the apparatus and method of the present invention, rapid and accurate stylus positioning and alignment with respect to a turntable is readily accomplished.